Was X superior in the past? No doubt about it, 100% agree. But unfortunately 2 things happened: 1) We (the X community) started to rest on our laurels and we get burned because of it. 2) The X protocol wasn't updated. We worked around it, extended it. We were treating symptoms instead of treating the problem.
There's been a lot of hostility towards X for a couple reasons.
1) Games are coming to Linux now, games adjust the resolution to ensure a smooth experience. This shined a bright light on the fact that X has a hard time (Though not impossible) with adjusting the resolution dynamically. With Wayland this get fixed by applying black borders like windows does.
2) Multi-monitor, and by extension multi-GPU is a MESS under X.
(Gotta run, ill post the end to this when I get back)